In fixed flame disposable lighters, manufacturing inconsistencies caused significant deviations of the flow rate of the fuel from the desired rate. Moreover, the influence of the gas vapor pressure has a more significant effect on the flame height when the temperature increases. Since the manufacturing inconsistencies of the metering material and the temperature influence are compounded, the user is frequently startled by an unexpectedly high flame. This represents a substantial safety problem because a startle reaction of the user might cause accidents. In other instances, the flame is unexpectedly low, in which case the lighter may be ineffective.
To attempt to resolve this problem, a majority of the low priced disposable lighters offered on the world market have a mechanism which permits the user to control the flame height. As a result, the manufacturing costs are increased, and the safety problem is still not solved because the necessity of reducing the flame height is recognized only after the startled reaction.
In the mass production of lighters without flame regulating devices, an important problem resides in controlling the flame height in such a manner that the flame height does not deviate more than plus or minus (i.e. +/-) 10% as compared to a desired value under equal temperature conditions. However, due to the temperature dependency of the vapor pressure in the lighter fuel tank, the amount of gas discharged inevitably increases. Thus the flame height increases with rising temperature.
For example, assuming a normal flame with a height of 25 mm at 25.degree. C. and 2.5 bars pressure, a temperature increase to 50.degree. C. results in an increase of the pressure to 5 bars when isobutane gas is used. This, as well as an additional, nonlinear, increased permeability of the metering material caused for example, by thermal expansion, leads to an increase of the flame height to 50 to 70 mm. If the observed change of the flame height at a desired temperature change is defined as flame index, and if the index value 1 is assigned to an increase of the flame from 25 to 50 mm when the temperature rises from 25.degree. to 50.degree. C., a flame height increase from 25 to 70 mm would correspond to a flame index of 1.8.
Experience has shown that in known lighters the aging in the unused state additionally leads to an irreversible change of the original flame height. This is particularly true when the lighters are subjected to changing or extreme ambient conditions, and when the metering material and its supporting structure have different thermal expansion rates.
Also, a flickering of the flames can be frequently observed. This is particularly true for pocket lighters which are subjected to very different temperatures and are frequently in a completely undefined carrying position immediately prior to being used.
My U.S. Pat. No. 4,496,309 resolves this problem within the framework of non-adjustable lighters. The content of this patent is expressly incorporated herein by reference.
The present invention avoids the disadvantages described hereinabove by providing a lighter with flame adjustability, combined with consistent and stable gas flow and reduced production costs.